The present invention relates generally to a wood replacement material, and more particularly, to a foam composite wood replacement material. The present invention will be described primarily with reference to wood flour/polyvinyl chloride (PVC) foam composites. However, the present invention includes several different formulations and material composites including, but not limited to, PVC formulations that include an inorganic filler in addition to the cellulosic material.
The supply of natural woods for construction and other purposes is dwindling. As a result, many are concerned about conserving the world""s forests, and the cost of natural woods has risen. In light of these factors, a tremendous demand has developed in recent years for cellulosic/polymer composites that exhibit the look and feel of natural woods.
Cellulosic/polymer composites are used as replacements for all-natural wood, particle board, wafer board, and other similar materials. For example, U.S. Pat. Nos. 3,908,902, 4,091,153, 4,686,251, 4,708,623, 5,002,713, 5,055,247, 5,087,400, and 5,151,238 relate to processes for making wood replacement products. As compared to natural woods, cellulosic/polymer composites offer superior resistance to wear and tear. In particular, cellulosic/polymer composites have enhanced resistance to moisture. In fact, it is well known that the retention of moisture is a primary cause of the warping, splintering, and discoloration of natural woods. Moreover, cellulosic/polymer composites may be sawed, sanded, shaped, turned, fastened, and finished in the same manner as natural woods. Therefore, cellulosic/polymer composites are commonly used for applications such as interior and exterior decorative house moldings, picture frames, furniture, porch decks, deck railings, window moldings, window components, door components, roofing structures, building siding, and other suitable indoor and outdoor items.
Cellulosic/polymer foam composites can be an alternative to cellulosic/polymer solid composites. Cellulosic/polymer foam composites use significantly less polymer material than cellulosic/polymer solid composites. Therefore, in light of the ever increasing cost of polymer materials such as PVC, cellulosic/polymer foam composites can offer substantial cost savings.
Cellulosic/polymer foam composites commonly include foaming or blowing agents to facilitate the foaming process. However, such agents also increase the difficulty of adding cellulosic fillers. In particular, cellulosic fillers absorb moisture thereby increasing the viscosity of the composite. Moreover, cellulosic fillers do not foam. Consequently, the other materials foam around the cellulosic fillers.
These properties of cellulosic fillers can adversely affect the appearance, strength, and durability of a resultant product made of a cellulosic/polymer foam composite. As a result, a need exists for an improved cellulosic/polymer foam composition that can be shaped into a resultant product having desired appearance, strength, durability, and weatherability. A need also exists for an improved method of making such a cellulosic/polymer foam composite.
The present invention satisfies some or all of these needs. The present invention provides cellulosic/polymer foam composite materials that can be produced in a commercially reasonable environment. One example of the present invention is a cellulosic/PVC foam composite. The cellulosic/polymer foam compositions of the present invention can be processed and shaped into resultant products having desired appearance, strength, durability, and weatherability. Also, the present invention provides improved methods of making such cellulosic/polymer foam composites.